A Randomized Study of Single Shot vs 24hr vs 48hr Continuous Adductor Canal Block for Postoperative Analgesia After Total Knee Arthroplasty

If the patient is willing to participate and signs the consent, he/she will be randomized to one of the three treatment groups:

1. Single shot block
2. 24 hour catheter
3. 48 hour catheter

The choice of anesthetic technique will be at the discretion of the anesthesiologist. In our institution we usually advocate for spinal anesthesia for total knee arthroplasty. All patients will receive their multimodal perioperative pain protocol (MP3) medication as per protocol in the patient receiving area (400 mg of gabapentin, 200 mg of Celecoxib, and 1gm of acetaminophen).

Patients will be monitored during block performance with standard ASA monitors. All patients will be receiving 2 L of oxygen via a nasal cannula. Sedatives will be titrated to effect. Midazolam 1-2 mg, and fentanyl 50-100 mcg will be used for sedation.

Block time out will be preformed according to standard operating procedure. All blocks will be done under ultrasound guidance. Sonosite S nerve machine will be used with a high frequency linear (HFL) US probe with 6-13 MHZ frequency. Both single shot and continuous adductor canal block will be performed according to the standard operating practices in our department 4. Ultrasound survey at the medial part of the thigh will take place, halfway between the superior anterior iliac spine and the patella. In a short axis view, the femoral artery will be identified underneath the sartorius muscle, with the vein just inferior and the saphenous nerve just lateral to the artery. The needle will be introduced in-plane and 2 to 3 mL of local anesthesia bolus will be used to verify correct placement of the needle in the vicinity of the saphenous nerve in the adductor canal.